WO2011064633A1

WO2011064633A1 - Method of producing molded article for use in beam path of radar device, molded article for use in beam path of radar device

Info

Publication number: WO2011064633A1
Application number: PCT/IB2010/002713
Authority: WO
Inventors: Fumitaka Yoshinaga; Takeshi Bessho
Original assignee: Toyota Jidosha Kabushiki Kaisha
Priority date: 2009-11-30
Filing date: 2010-10-25
Publication date: 2011-06-03
Also published as: JP2011112596A

Abstract

A surface of a transparent resin substrate (2) is subjected to an oxidation treatment to form a modified layer (11) therein, the modified layer (11) being applied with catalyst metal particle to form a resin-metal composite layer (3) in which the catalyst metal particles are dispersedly formed to the modified layer (11). A surface of the resin-metal composite layer (3) is subjected to electroless plating to form a discontinuous metal layer (4) in which a plating metal (21) is deposited in a dispersed state.

Description

METHOD OF PRODUCING MOLDED ARTICLE FOR USE IN BEAM PATH OF RADAR DEVICE, MOLDED ARTICLE FOR USE IN BEAM PATH OF RADAR DEVICE

BACKGROUND OF THE INVENTION

1 . Field of the Invention

[0001] The present invention relates to a method of producing a molded article that is disposed and used in a beam path of a radar device which is disposed, for example, behind a front grill of a vehicle, to a molded article that is disposed and used in a beam path of such a radar device, and to a radar mechanism that is provided with such a molded article.

2. Description of the Related Art

[0002] A radar device that measures, for example, a distance between a vehicle and an obstacle in front of the vehicle or a distance between a vehicle and another vehicle that travels ahead is preferably located in a center front position of the vehicle in order to obtain its optimum performance. Thus, an antenna is mounted near a front grill of the vehicle. From the standpoint of design, such an antenna is desired not to be visible from the outside. Accordingly, the radar device that is installed in a vehicle is located behind the front grill thereof.

[0003] An emblem of a vehicle manufacturer and an ornament specific to the vehicle are mounted on a front grill. Thus, a radio wave such as a millimeter wave from a radar device travels along the following beam path. That is, the wave is emitted toward the front via the front grill, etc., is reflected by an object such as a vehicle that travels ahead or an obstacle that is present ahead, and then returns to the radar device through the front grill, etc.

[0004] Therefore, in the portions at which the front grill, etc. are located in the beam path of the radar device, it is preferable to use a material and a paint that have a low wave transmission loss and can provide a desired beautiful appearance.

[0005] Thus, in one conventional technology, a window portion has been provided in that portion of the front grill which corresponds to the location at which the radar device is installed and a radio wave transmitting cover has been inserted in such a window portion so that a sense of unity can be established between the window and the front grill body (see, for example, Japanese Patent Application Publication No. 2000- 159039 (JP-A-2000- 159039)).

[0006] The radio wave transmitting cover disclosed in JP-A-2000- 159039 is formed of a laminate of a plurality of resin layers with irregularities. The covering component has a metal layer that is vapor-deposited between the resin layers with irregularities so that the metal layer can give the impression as if the fins of the front grill were continuously existing in the radio wave transmitting cover.

[0007] As a metal that is vapor-deposited on the radio wave transmitting cover, indium is used. When indium is vapor-deposited on a material to be deposited, indium is deposited on the surface of the material to be deposited not in the form of a uniform film but in the form of fine islands. Specifically, when indium is deposited on the material to be deposited, the surface of the deposited material is in such a state that fine island-like indium deposited portions and non-deposited portions exist together in a finely mixed state. In this case, a radio wave can be transmitted through the non-deposited portions, and yet the surface of the deposited member is viewed as a member that has a metallic luster because of the fine island-like indium deposited portions.

[0008] A technology that belongs to the same technical field as that of the above-described JP-A-2000- 159039 and that forms a metal layer by a dry method similar to that adopted in JP-A-2000- 159039, such as vapor deposition or sputtering, is disclosed in Japanese Patent No. 3,366,299 and Japanese Patent No. 3,597,075.

[0009] However, a workpiece must be set in a vacuum chamber in order to form a metal layer thereon by a dry method. Therefore, when a metal layer that can pass a radio wave therethrough is formed on a surface of a workpiece by using a dry method such as vapor deposition or sputtering as disclosed in JP-A-2000- 159039, JP-B-3366299 and JP-B-3597075, large scale equipment and apparatuses are required. Further, a process time becomes long, costs are increased, and large scale production is difficult.

[0010] Additionally, owing to its characteristics, the dry method enables to form a metal layer that has uniform thickness throughout the entirety of a surface on which the metal layer is desired to be formed, when the surface is two-dimensional and has a simple flat shape. When the surface on which a metal layer is to be formed has a complicated three-dimensional stereo shape, however, it is impossible to form a metal layer that has a uniform thickness throughout the entirety of the surface with the dry method.

SUMMARY OF THE INVENTION

[0011] The present invention provides a method of producing a molded article that is disposed and used in a beam path of a radar device, which is capable of forming a metal layer that has a uniform thickness and can pass a radio wave therethrough, on a molded article that has a complicated three-dimensional stereo shape, which requires only simple equipment, a short process time and low costs and which enables large scale production. The present invention also provides a molded article that is disposed and used in a beam path of such a radar device, and a radar mechanism that is provided with such a molded article.

[0012] A first aspect of the present invention relates to a method of producing a molded article that is disposed and used in a beam path of a radar device. The method includes: an oxidation treatment step in which a surface of a transparent resin substrate is subjected to an oxidation treatment to form a modified layer therein; a catalyst application treatment step in which catalyst metal particles are applied to the modified layer to form a resin-metal composite layer in which the catalyst metal particles are dispersedly adsorbed to the modified layer; and an electroless plating treatment step in which a surface of the resin-metal composite layer is subjected to electroless plating to form a discontinuous metal layer in which a plating metal is deposited in a dispersed state.

[0013] According to this method, since a discontinuous metal layer in which a plating metal is deposited in a dispersed state is formed on a surface of the resin-metal composite layer, a radio wave from a radar device can pass through interstices of the dispersed plating metal and can enter and exit therethrough and, yet, the molded article after the electroless plating treatment step may be viewed from outside as a molded article that has a metallic luster.

[0014] Further, according to this method, since a discontinuous metal layer is formed by the electroless plating treatment, molded articles that is disposed and used in a beam path of a radar device may be produced on a production line using simple equipment and may be produced with a short process time on a large scale at low costs.

Additionally, even when the transparent resin substrate has a complicated three-dimensional stereo shape, a discontinuous metal layer that has a uniform thickness throughout its surface may be formed without being influenced by orientation of its surfaces, unlike in the case of vapor deposition or sputtering.

[0015] In the oxidation treatment step of the above production method, the transparent resin substrate may be subjected to an ozone treatment by using an ozone solution to form the modified layer.

[0016] According to the above constitution, the procedures from the oxidation treatment step to the electroless plating treatment step may be carried out in a wet process.

Therefore, the process time may be further shortened so that the process cost can be further reduced.

[0017] In the above method, the ozone concentration of the ozone solution may be 20 ppm or more. In the above method, a polar solvent may be used as a solvent for the ozone solution. In the above ozone treatment, the transparent resin substrate may be contacted with the ozone solution for 2 minutes or more. In the above ozone treatment, the transparent resin substrate may be contacted with the ozone solution for 30 minutes or less.

[0018] In the electroless plating treatment step of the above method, the transparent resin substrate may be immersed in a plating liquid, and the transparent resin substrate and the plating liquid may then be left.

[0019] According to this constitution, since the transparent resin substrate is immersed in a plating liquid, and the transparent resin substrate and the plating liquid areleft, it is possible to prevent an increase of deposition rate of the plating metal which might otherwise occur due to circulation of the plating liquid or movement of the transparent resin substrate in the plating liquid. Accordingly, the plating metal can deposit, in a dispersed state, to a surface of the resin-metal composite layer, so that discontinuity can be positively created in the discontinuous metal layer.

[0020] In the electroless plating treatment step of the above method, the plating liquid may be maintained in circulation when the transparent resin substrate is not immersed therein.

[0021] According to this constitution, since the plating liquid is maintained in circulation when the transparent resin substrate is not immersed therein, it is possible to prevent the plating liquid from self-decomposing which might otherwise occur due to insufficient liquid circulation and to improve the service life of the plating liquid.

[0022] The method may further comprise, an alkali treatment step between the oxidation treatment step and the catalyst application treatment step; and in the alkali treatment step, the modified layer may be brought into contact with a solution that contains an alkaline component. In the above method, the catalyst metal particles may comprise tin, and the modified layer may be contacted with a metal compound solution, that contains the catalyst metal particles, to adsorb the metal compound solution and to form the resin-metal composite layer in the catalyst application treatment step. In this case, the method may further comprise an activation step in which tin is removed from the metal compound solution that has been adsorbed to the modified layer.

[0023] A second aspect of the present invention relates to a molded article that is disposed and used in a beam path of a radar device. This molded article includes a transparent resin substrate, a resin-metal composite layer that is formed of catalyst metal particles which are dispersedly formed on a surface of the transparent resin substrate, and a discontinuous metal layer that is formed of a plating metal that is deposited in a dispersed state on a surface of the resin-metal composite layer by electroless plating.

[0024] A third aspect of the present invention relates to a radar mechanism. The radar mechanism includes a molded article which comprises a transparent resin substrate, a resin-metal composite layer that is formed of catalyst metal particles which are dispersedly formed on a surface of the transparent resin substrate, and a discontinuous metal layer that is formed of a plating metal that is deposited in a dispersed state on a surface of the resin-metal composite layer by electroless plating, and a radar device, wherein the transparent resin substrate, the resin-metal composite layer, and the discontinuous metal layer are located in a beam path of the radar device.

[0025] According to the above-described second and third aspects, since the discontinuous metal layer in which a plating metal is deposited in a dispersed state is formed on a surface of the resin-metal composite layer, a radio wave from a radar device can transmit through interstices of the dispersed plating metal and can enter and exit therethrough and, yet, the molded article may be viewed from outside as a molded article that has a metallic luster.

[0026] Further, according to the above-described second and third aspects, since the discontinuous metal layer is formed by an electroless plating treatment, molded articles that is disposed and used in a beam path of a radar device may be produced on a production line using simple equipment and may be produced with a short process time on a large scale at low costs. Additionally, even when the transparent resin substrate has a complicated three-dimensional stereo shape, the discontinuous metal layer that has a uniform thickness throughout its surface may be formed.

[0027] Further, according to the above-described second and third aspects, since a discontinuous metal layer is formed by the electroless plating treatment, molded articles that is disposed and used in a beam path of a radar device may be produced on a production line using simple equipment and may be produced with a short process time on a large scale at low costs. Additionally, even when the transparent resin substrate has a complicated three-dimensional stereo shape, a discontinuous metal layer that has a uniform thickness throughout its surface may be formed without being influenced by orientation of its surfaces, unlike in the case of vapor deposition or sputtering. BRIEF DESCRIPTION OF THE DRAWINGS

[0028) The features, advantages, and technical and industrial significance of this invention will be described in the following detailed description of example embodiments of the invention with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:

FIG. 1 is a view that schematically illustrates a cross-sectional structure of a molded article according to the present invention;

FIG. 2 is a flow chart that shows a production method for a molded article for use in a beam path of a radar device according to the present invention;

FIG. 3 is a flow chart that explains a plating treatment step according to the present invention; and

FIG. 4 is a view that schematically illustrates a surface of a molded article for use in a beam path of a radar device according to the present invention. DETAILED DESCRIPTION OF EMBODIMENTS

[0029] FIG. 1 is a view that schematically illustrates a cross-sectional structure of a molded article that is disposed and used in a beam path of a radar device according to an embodiment of the present invention.

[0030] Referring to FIG. 1 , designated as 1 is a molded article that is disposed and used in a beam path of a radar device (i.e., a molded article for use in a beam path of a radar device). The molded article 1 has a transparent resin substrate 2 (namely a resin substrate through which a radio wave can pass), a resin-metal composite layer 3 formed on a surface of the transparent resin substrate 2, and a discontinuous metal layer 4 formed on a surface of the resin-metal composite layer 3.

[0031] The transparent resin substrate 2 is a resin molded article that is formed into, for example, a front grill or emblem of a motor vehicle and is made of a transparent resin material.

[0032] The transparent resin substrate 2 is formed of a material that has low wave transmission loss and excellent dielectric properties. The dielectric properties may be expressed in terms of, for example, dielectric constant ε' and dielectric loss tan6. The transparent resin substrate 2 is preferably formed of a polycarbonate resin, an acrylic resin, or a cyclic polyolefin resin. A cyclic polyolefin resin (such as a polynorbornene- based resin or a polycyclohexene-based resin) that is one of the transparent resins usable for the transparent resin substrate 2 in the present invention is amorphous in nature and is excellent in transparency.

[0033] When a cyclic polyolefin resin that has low wave transmission loss and excellent dielectric properties is used as a transparent resin for the transparent resin substrate 2, the wettability of the transparent resin substrate 2 may be improved by subjecting a surface of the cyclic polyolefin resin substrate to a plasma etching treatment and/or a treatment with high concentration ozone water, so that the adhesion thereof to a palladium and/or palladium alloy layer is significantly improved.

[0034] The transparent resin of the transparent resin substrate 2 may be compounded with other polymer or polymers, if necessary. Examples of such other polymers include rubbers and other thermoplastic resins. As the rubbers, there may be mentioned, for example, natural rubbers, polybutadiene rubbers, polyisoprene rubbers, acrylonitrile-butadiene copolymer rubbers, styrene-butadiene copolymer rubbers, styrene-isoprene copolymer rubbers, styrene-butadiene-isoprene copolymer rubbers, hydrogenated products of diene-based rubbers, saturated polyolefin rubbers such as ethylene-a-olefin copolymers (e.g., ethylene-propylene copolymers), ethylene-propylene- diene copolymers, a-olefin-diene copolymers, urethane rubbers, silicone rubbers, polyether-based rubbers, acryl rubbers, styrene-butadiene-styrene block copolymer rubbers, thermal plastic elastomers such as styrene-isoprene-styrene block copolymer rubbers, hydrogenated thermoplastic elastomers, urethane-based thermoplastic elastomers, polyamide-based thermoplastic elastomers, and 1 ,2-polybutadiene-based thermoplastic elastomers.

[0035] As the other thermoplastic resins, there may be mentioned, for example, polyolefins such as low-density polyethylenes, high-density polyethylenes, linear low density polyethylenes (LLDPE), very low density polyethylenes, polypropylenes, syndiotactic polypropylenes, polybutenes and polypentene, polyesters such as polyethylene terephthalates and polybutylene terephthalates, polyamides such as nylon 6 and nylon 66, ethylene-ethyl acrylate copolymers, ethylene-vinyl acetate copolymers, polystyrenes, syndiotactic polystyrenes, polyphenylene sulfides, polyphenylene ethers, aromatic polyamides, and polycarbonates. These other thermoplastic resins may be used singly or in combination with two or more thereof. The compounding amount of the other polymer or polymers is such that radio wave transmitting property, durability, and abrasion resistance of the transparent resin are not lost; namely, not more than 50% by mass, preferably not more than 30% by mass, relative to the transparent resin.

[0036] The transparent resin of the transparent resin substrate 2 may be compounded with an additive or additives, if necessary. Examples of the additives include an antioxidant, an ultraviolet absorbent, a lubricant, an anti-fogging agent, an anti-mist agent, a plasticizer, a pigment, a near-infrared absorbent, and an antistatic agent.

[0037] The molded body of the transparent resin substrate 2 can be manufactured by a customarily employed method such as a melt molding method or a solvent casting method. Examples of the melt molding method include a melt extrusion method such as a T-die method and an inflation molding method, a calendar method, a thermal pressing method, and an injection molding method. In the solvent casting method, a liquid body in which individual components are dissolved or dispersed in a solvent is cast on a support, and then the solvent is evaporated. Examples of the solvent used for the solvent casting method include aromatic hydrocarbons such as toluene, xylene and, mesitylene, alicyclic hydrocarbons such as cyclohexane and decalin, and halogen compounds such as methylene chloride, chloroform, chlorobenzene, and dichlorobenzene. The concentration of the transparent resin in the liquid body is generally 0.1 to 60% by mass, preferably 3 to 45% by mass. Examples of the method for casting the liquid body on the support include bar coaters, doctor blades, Mayer bars, roll coaters, die coaters, spraying, air-knife coating, spin coating, and dip coating. The removal of the solvent may be conducted by any conventional method, and the solvent is evaporated until the content of residual solvent is 5% by mass or less, preferably 1 % by mass or less, more preferably 0.5% by mass or less.

[0038] The resin-metal composite layer 3 is formed on a surface of the transparent resin substrate 2 by providing thereon catalyst metal particles, such as of palladium, in a dispersed state. The resin-metal composite layer 3 is formed by dispersedly adsorbing catalyst metal particles to a modified layer 1 1 that has been formed by an oxidation treatment of the transparent resin substrate 2. The resin-metal composite layer 3 has a thickness of, for example, 20 to 100 nm.

[0039] The discontinuous metal layer 4 is formed of a plating metal 21 , such as nickel, that is deposited in a dispersed state on the resin-metal composite layer 3 by electroless plating. The plating metal 21 is deposited in a dispersed state on a surface of the resin-metal composite layer 3. A radio wave from a radar device can pass through interstices of the plating metal 21 and, therefore, can enter and exit through the discontinuous metal layer 4. The discontinuous metal layer 4 is arranged in a dispersed state so as to be viewed as having a metallic tone (see, for example, FIG. 4).

[0040] The natural light that incidents from outside on the molded article 1 for use in a beam path of a radar device passes through the transparent resin substrate 2 and the resin-metal composite layer 3 and is reflected on the metal layer 4. Therefore, the molded article 1 for use in a beam path of a radar device is viewed from outside as a member that has a metallic luster.

[0041] The molded article 1 for use in a beam path of a radar device is formed with the discontinuous metal layer 4 in which the plating metal 21 is deposited in a dispersed state on a surface of the resin-metal composite layer 3. As a consequence, a radio wave from a radar device can pass through interstices of the dispersed plating metal 21 and, therefore, can enter and exit through the molded article 1 . Yet, the molded article 1 may be viewed from outside as a molded article that has a metallic luster.

[0042] Thus, since the discontinuous metal layer 4 is formed by electroless plating, molded articles 1 for use in a beam path of a radar device may be produced on a production line using simple equipment and may be produced with a short process time on a large scale at low costs. Further, the discontinuous metal layer 4 may be formed of a plating metal such as nickel, the material cost may be reduced as compared with indium.

Additionally, even when the transparent resin substrate 2 has a complicated three-dimensional stereo shape, the discontinuous metal layer 4 that has a uniform thickness may be formed on its surface by electroless plating.

[0043] A method of the production of a molded articles 1 for use in a beam path of a radar device that has the above-described configuration will be next described with reference to the flow chart shown in FIG. 2.

[0044] The method for the production of a molded article 1 for use in a radar device beam path includes an oxidation treatment step S I , an alkali treatment step S2, a catalyst application treatment step S3, an activation treatment step S4, and an electroless plating treatment step S5.

[0045] In the oxidation treatment step S I , a surface of the transparent resin substrate 2 is subjected to an oxidation treatment to form a modified layer 1 1 therein.

The modified layer 1 1 may be formed by, for example, an ultraviolet ray (UV) irradiation treatment, a plasma treatment, an ultraviolet ray irradiation treatment that is preceded by application of a photo catalyst, or an ozone treatment using an ozone solution or an ozone gas. Above all, the ozone treatment using an ozone solution is particularly preferred.

[0046] An ozone treatment using an ozone solution can permit the procedures from the oxidation treatment step S I to the electroless treatment step S5 to be performed in a wet process, so that the process time can be shortened as compared with other processes and can be carried out with reduced costs.

[0047] In the ozone treatment step, the transparent resin substrate 2 is subjected to a treatment with an ozone solution to form, on a surface of the transparent resin substrate 2, a modified layer 1 1 that has polar groups. The modified layer 1 1 is a layer that is formed in a surface of the transparent resin substrate 2 and has pores having a size of a nano (nm) level or a size smaller than the nano level. The treatment with the ozone solution may be carried out by, for example, an immersion method in which the transparent resin substrate 2 is immersed in the ozone solution, or a spray method in which the ozone solution is sprayed onto the transparent resin substrate 2. The immersion method in which the transparent resin substrate 2 is immersed in the ozone solution is preferred because ozone is less likely to be released from the ozone solution as compared with application by spraying.

[0048] The ozone concentration in the ozone solution has a great influence on the surface activation of the transparent resin substrate 2. An ozone concentration of about 10 ppm or more gives an effect of activation, and an ozone concentration of 20 ppm or more exponentially increases the activation effect and allows a short time treatment. It is preferred that the ozone concentration be high rather than low, because deterioration of the ozone solution may be likely to occur when the concentration is low. As a result of the oxidation by ozone in the ozone solution, polar groups such as OH groups, CO groups, and COOH groups are formed in the modified layer.

[0049] While the ozone solution usually uses water as a solvent, an organic or inorganic polar solvent may also be preferably used as the solvent because the treatment time may be further shortened. Examples of the organic polar solvent include alcohols such as methanol, ethanol, and isopropyl alcohol, N,N-dimethylformamide, Ν,Ν-dimethylacetamide, dimethylsulfoxide, N-methylpyrrolidone, hexamethyl- phosphoramide, organic acids such as formic acid and acetic acid, and mixed solvents of these solvents with water or alcohol-type solvents. Examples of the inorganic polar solvent include inorganic acids such as nitric acid, hydrochloric acid, and hydrofluoric acid.

[0050] In theory, the higher the treatment temperature in the ozone treatment step, the higher is the reaction rate. However, the higher the temperature, the lower becomes the solubility of ozone in the ozone solution. In order to maintain the ozone concentration of the ozone solution of 40 ppm or more at a temperature that exceeds 40°C, it is necessary to increase the pressure of the treatment atmosphere above the atmospheric pressure, so that a large apparatus is needed. The temperature at which the treatment is carried out may be about room temperature.

[0051] The time of contact between the ozone solution and the transparent resin substrate 2 in the ozone treatment, which is dependent on the type of the resin, is preferably 2 to 30 minutes. A contact time of less than 2 minutes makes it difficult for the effect of the ozone treatment to develop even with the ozone concentration of 20 ppm or more. A contact time of more than 30 minutes may cause deterioration of the transparent resin substrate 2.

[0052] In the ozone treatment, it is preferable to irradiate UV rays in the state where a surface of the transparent resin substrate 2 is maintained in contact with an ozone solution with a high concentration. The UV rays to be emitted preferably have a wavelength of 3 10 nm or less, more preferably 260 nm or less, still more preferably about 1 50 to about 200 nm. The amount of ultraviolet irradiation is preferably 50 mJ/cm or more. As a light source that can emit such ultraviolet rays, a low-pressure mercury lamp, a high-pressure mercury lamp, an excimer laser, a barrier discharge lamp, or a microwave electrodeless discharge lamp may be used.

[0053] When the transparent resin substrate 2 is irradiated with UV rays while being immersed in an ozone solution, irradiation may be conducted in the state where the UV ray source is placed in the ozone solution. Alternatively, the irradiation may be conducted from above the liquid level of the ozone solution. Further, when a vessel containing the ozone solution is made of a UV ray permeable material such as transparent quartz, the irradiation may be conducted from outside the vessel.

[0054] In the alkali treatment step S2, the modified layer 1 1 after the oxidation treatment step S 1 is brought into contact with a cleaner conditioner solution that contains at least an alkaline component. As a result of the alkali treatment, the wettability of the modified layer 1 1 is improved so that the adhesion of catalyst metal particles in the succeeding catalyst application treatment step S3 can be significantly improved.

[0055] The alkaline component has a function to make a surface of the modified layer 1 1 soluble at the molecular level in water and to remove an embrittled layer on the surface of the modified layer 1 1 , so that an increased number of polar groups are exposed on the surface of the modified layer 1 1 . Therefore, in the succeeding catalyst application treatment step S3, metal fine particles may be formed in a larger amount.

[0056] As the alkaline component, a substance capable of dissolving a surface of the modified layer 1 1 at the molecular level and of removing the resulting embrittled layer may be used, and sodium hydroxide, potassium hydroxide, lithium hydroxide, or the like can be used.

[0057] The time of contact between the cleaner conditioner solution and the modified layer 1 1 , which is not specifically limited, is preferably at least 1 minute at 10°C. When the time of contact is too short, the amount of a surfactant that adsorbs to the polar groups may be insufficient. However, when the time of contact is too long, the alkaline component may dissolve the exposed layer. The contact time of about 1 to about 10 minutes is sufficient. Also, it is preferable to use a higher contact temperature since the time of contact can be shortened with the higher contact temperature. A contact temperature of about 10 to about 70°C is sufficient.

[0058] In the catalyst application treatment step S3, the modified layer 1 1 is treated to apply catalyst metal particles thereto and to form a resin-metal composite layer 3. The resin-metal composite layer 3 is formed by dispersedly adsorbing the catalyst metal particles to the modified layer 1 1 . More specifically, the modified layer 1 1 is brought into contact with a metal compound solution so that the metal compound solution that contains at least one of catalyst metal colloids and catalyst metal ions penetrates into the modified layer 1 1.

[0059] Since the modified layer 1 1 has been formed with polar groups by cleavage of the resin molecular chains, the catalyst metal colloids or ions adsorb to the polar groups, thereby to form the resin-metal composite layer 3.

[0060] As the metal compound solution, alkaline solutions that contain metal complex ions and acidic solutions that contain a metal colloid are known, and both types can be used. However, an alkaline metal compound solution that contains metal particles with a small diameter is preferably used. It is because the adhesion strength of the plating metal 21 is further improved due to its high permeability and high dispersibility into the modified layer 1 1. It should be noted that catalyst metal particles are those which function as a catalyst in the electroless plating treatment step. Palladium is generally used as the catalyst metal particles. A mixture of palladium and tin may be used as the metal compound solution.

[0061] To bring the modified layer 1 1 into contact with the metal compound solution, the metal compound solution may be applied, by spraying, to the surface of the transparent resin substrate 2 on which the modified layer 1 1 is formed, or the transparent resin substrate 2 may be immersed in the metal compound solution. By so doing, the metal compound solution diffuses from the surface of the modified layer 1 1 into the interior thereof, and the ions or colloids of the metal compound adsorb to the polar groups. The metal compound is then converted into fine catalyst metal particles of a nano-level size by a reduction reaction to form the resin-metal composite layer 3. The resin-metal composite layer 3 preferably has a thickness of 20 to 100 nm.

[0062] In the activation step S4, tin is removed from the metal compound solution that has been adsorbed to the modified layer 1 1 during the catalyst application treatment step S3. For example, by washing the surface (namely the resin-metal composite layer 3) of the transparent resin substrate 2 with hydrochloric acid, tin may be removed. The removal of tin may facilitate the deposition of a plating metal 21 in the succeeding electroless plating treatment step S5.

[0063] In the electroless plating treatment step S5, the transparent resin substrate 2 is immersed in a plating liquid so that a surface of the resin-metal composite layer 3 is subjected to electroless plating to form a discontinuous metal layer 4 in which the plating metal 21 is deposited in a dispersed state. The discontinuous metal layer 4 preferably has a layer thickness of in the range of 25 to 60 nm. The electroless plating may be carried out by, for example, immersing the transparent resin substrate 2 in a plating liquid at 40°C for 10 seconds.

[0064] When the immersing time is excessively long, the plating metal 21 continuously grows into a uniform film-like form and covers the surface of the resin-metal composite layer 3. The discontinuity of the discontinuously layer 4 is thus deteriorated so that there is a possibility that the radio wave transmitting property thereof, by which a radio wave from a radar device is allowed to pass therethrough, is deteriorated. Thus, the immersing time is controlled so that the plating metal 21 is deposited in a dispersed state by the plating treatment.

[0065] Electroless plating can be carried out in such a manner that a plating liquid is circulated, for example, by bubbling an oxygen-containing gas such as air through the plating liquid, by stirring the plating liquid, or by swingingly moving the material to be plated, in order to prevent self decomposition of the plating liquid and to stabilize the property of the plating liquid. In the present case, however, when the plating liquid is circulated, the deposition rate of the plating metal 21 is accelerated and continuously grows within a short period of time into a uniform film-like form, so that there is a possibility that the discontinuity of the discontinuous metal layer 4 is deteriorated.

[0066] In the electroless plating treatment step S5, therefore, the transparent resin substrate 2 and the plating liquid are allowed to stand quiescently, when the transparent resin substrate 2 is immersed in the plating liquid. Thus, it is possible to prevent an increase of deposition rate of the plating metal which might otherwise occur due to circulation of the plating liquid or swinging movement of the transparent resin substrate in the plating liquid. Accordingly, the plating metal can deposit, in a dispersed state, to a surface of the resin-metal composite layer 3, so that discontinuity can be positively created in the discontinuous metal layer 4.

[0067] In the electroless plating treatment step S5, the plating liquid is maintained in circulation, such as by bubbling or stirring, when the transparent resin substrate 2 is not immersed therein. Accordingly, it is possible to prevent the plating liquid from self-decomposing which might otherwise occur due to insufficient liquid circulation and to improve the service life of the plating liquid.

[0068] The plating liquid may be allowed to stand quiescently by, for example, stopping circulation, such as bubbling or stirring, of the plating liquid so as to positively prevent the plating liquid from flowing. The transparent resin substrate 2 may be allowed to stand quiescently by, for example, by fixing the position of the transparent resin substrate 2 while immersing the transparent resin substrate 2 in the plating liquid.

[0069] FIG. 3 is a flow chart that explains a plating method in the electroless plating treatment step S5.

[0070] First, in step S l l , adjustment of the chemical solution, temperature, pH and so on of an electroless plating bath is conducted. In step S I 2, liquid circulation of the plating liquid is carried out by bubbling, stirring or the like method. In step S I 3, the liquid circulation of the plating liquid is stopped and a workpiece (namely, transparent resin substrate 2) is then immersed in the plating liquid that has stopped moving, so that electroless plating is carried out while maintaining the plating liquid and transparent resin substrate 2 in a quiescent state. In step S I 4, the transparent resin substrate 2 is picked up from and taken out of the plating liquid and, in step S I 5, liquid circulation of the plating liquid is again started.

[0071] Then, as shown in step S I 6, when a plurality of such transparent resin substrates 2 are intended to be individually plated, the treatments from step S 13 to step 15 are repeatedly carried out until the plating treatment of all of them is completed. In this case, the adjustment treatment in step S l l is appropriately conducted between the repeated treatments.

[0072] The thus configured molded article 1 for use in a beam path of a radar device is formed with the discontinuous metal layer 4 in which the plating metal 21 is deposited in a dispersed state on a surface of the resin-metal composite layer 3. Therefore, a radio wave from a radar device can transmit through interstices of the dispersed plating metal 21 and can enter and exit the molded article 1 and, yet, the molded article 1 may be viewed from outside as a molded article that has a metallic luster.

[0073] Further, according to the above-described method for producing a molded article 1 for use in a beam path of a radar device, since the discontinuous metal layer 4 is formed by an electroless plating treatment, molded articles 1 for use in a beam path of a radar device may be produced on a production line using simple equipment and may be produced with a short process time on a large scale at low costs. Additionally, even when the transparent resin substrate 2 has a complicated three-dimensional stereo shape, the discontinuous metal layer 4 that has a uniform thickness throughout its surface may be formed without being influenced by orientation of its surfaces, unlike in the case of vapor deposition or sputtering. Therefore, with the above-described method, it is possible to produce a molded article 1 for use in a beam path of a radar device, which molded article exhibits radio wave transmitting property and has a metallic luster in the entire surface of its transparent resin substrate 2.

[Examples]

[0074] The present invention will be next described by way of examples.

[0075] ( 1 ) Oxidation treatment step

A transparent resin substrate 2 was immersed in an ozone water solution that had an ozone content of 40 ppm and subjected to an ozone treatment therein at room temperature for 8 minutes to form a modified layer 1 1 on a surface of the transparent resin substrate 2.

[0076] (2) Alkali treatment step

The transparent resin substrate 2 after the oxidation treatment step was immersed for 2 minutes in a cleaner conditioner solution (content of NaOH: 50 g/L, content of sodium lauryl sulfate: l g/L) that was warmed to 50°C and was treated therewith to improve the wettability of a surface of the transparent resin substrate 2.

[0077] (3) Catalyst application treatment step

The transparent resin substrate 2 after the alkali treatment was washed with water, dried, and then immersed in a mixed solution that contained 0.1 % by weight of palladium chloride, 5% by weight of tin chloride, and 3N hydrochloric acid at 32°C for 2 minutes to form a resin-metal composite layer 3.

[0078] (4) Activation treatment step

The transparent resin substrate 2 after the catalyst application treatment step was washed and treated with IN hydrochloric acid to remove the tin chloride from the resin-metal composite layer 3.

[0079] (5) Electroless plating treatment step

The transparent resin substrate 2 after the activation treatment step was placed in an electroless plating bath and immersed in a nickel plating liquid at 40° for 10 seconds to deposit nickel on the resin-metal composite layer 3 by electroless plating and to form a discontinuous metal layer 4.

[0080] FIG. 4 is a view that schematically illustrates a surface of a molded article for use in a beam path of a radar device which molded article was formed by the method described in the present example. As shown in FIG. 4, in the molded article 1 for use in a beam path of a radar device, a plating metal 21 that includes nickel is deposited in a dispersed state on a surface of a resin-metal composite layer 3. The dispersed plating metal 21 allows a radio wave from a radar device to pass through interstices thereof and to enter and exit therethrough and, yet is arranged in a dispersed state so as to be viewed as having a metallic tone.

[0081] The present invention is not limited to the above-described embodiments but may be variously modified without departing from the gist of the invention.

Claims

1 . A method of producing a molded article that is disposed and used in a beam path of a radar device, characterized by comprising:

an oxidation treatment step in which a surface of a transparent resin substrate is subjected to an oxidation treatment to form a modified layer therein;

a catalyst application treatment step in which catalyst metal particles are applied to the modified layer to form a resin-metal composite layer in which the catalyst metal particles are dispersedly adsorbed to the modified layer; and

an electroless plating treatment step in which a surface of the resin-metal composite layer is subjected to electroless plating to form a discontinuous metal layer in which a plating metal is deposited in a dispersed state.

2. The production method according to claim 1 , wherein,

in the oxidation treatment step, the transparent resin substrate is subjected to an ozone treatment by using an ozone solution to form the modified layer.

3. The production method according to claim 2, wherein

the ozone solution has an ozone concentration of 20 ppm or more.

4. The production method according to claim 2 or 3, wherein

a polar solvent is used as a solvent for the ozone solution.

5. The production method according to any one of claims 2 to 4, wherein,

in the ozone treatment, the transparent resin substrate is contacted with the ozone solution for 2 minutes or more.

6. The production method according to any one of claims 2 to 5, wherein,

in the ozone treatment, the transparent resin substrate is contacted with the ozone solution for 30 minutes or less.

7. The production method according to any one of claims 1 to 6, wherein,

in the electroless plating treatment step, the transparent resin substrate is immersed in a plating liquid, and the transparent resin substrate and the plating liquid are then left.

8. The production method according to claim 7, wherein,

in the electroless plating treatment step, the plating liquid is maintained in circulation when the transparent resin substrate is not immersed therein.

9. The production method according to any one of claims 1 to 8, further comprising, an alkal i treatment step between the oxidation treatment step and the catalyst application treatment step; and in the alkali treatment step, the modified layer is brought into contact with a solution that contains an alkaline component.

10. The production method according to any one of claims 1 to 9, wherein

the catalyst metal particles comprise tin, and

in the catalyst application treatment step, the modified layer is contacted with a metal compound solution that contains the catalyst metal particles to adsorb the metal compound solution and to form the resin-metal composite layer, the production method further comprising

an activation step in which tin is removed from the metal compound solution that has been adsorbed to the modified layer.

1 1 . A molded article that is disposed and used in a beam path of a radar device, characterized by comprising:

a transparent resin substrate,

a resin-metal composite layer that is formed of catalyst metal particles which are dispersedly formed on a surface of the transparent resin substrate, and a discontinuous metal layer that is formed of a plating metal that is deposited in a dispersed state on a surface of the resin-metal composite layer by electroless plating.

12. A radar mechanism characterized by comprising:

a molded article which comprises a transparent resin substrate, a resin-metal composite layer that is formed of catalyst metal particles which are dispersedly formed on a surface of the transparent resin substrate, and a discontinuous metal layer that is formed of a plating metal that is deposited in a dispersed state on a surface of the resin-metal composite layer by electroless plating, and

a radar device

wherein the transparent resin substrate, the resin-metal composite layer, and the discontinuous metal layer are located in a beam path of the radar device.